I refer to Beck's plots occasionally. We don't plant one kernel/seed of their product, but I read their research plot stuff. I'm surprised more companies don't have these...but then I'm asking for overhead to be raised even higher.

Looks like if you read Beck's stuff, it's pretty much a toss up on 7.5-15-30" sb rows. You can read for yourself though:

http://www.beckshybrids.com/research/2005/pg65.pdf

Re. being concerned about seed cost...yes-that's certainly one of annual concerns. We fully understand that seed salesmen would like us to overlook it entirely...but that won't happen. It's a factor in the equation....a consideration. However, probably a bigger factor is machinery cost. I think most of those asking about 30" rows would envision using their corn planter for both corn & beans. That would have many advantages, I think.